1 #!/usr/bin/env python 2 3 import sqlalchemy 4 from sqlalchemy import create_engine 5 from sqlalchemy.ext.declarative import declarative_base 6 from sqlalchemy import Column,Integer,String,DATE,Enum,ForeignKey 7 from sqlalchemy.orm import sessionmaker,relationship 8 9 # 创建连接 echo=True 就会打印出所有过程信息10 engine = create_engine("mysql+pymysql://root:root@localhost/testuser",encoding="utf-8",echo=True)11 12 #13 Base = declarative_base() # 生成orm基类14 15 class Student(Base):16 __tablename__ = "student"17 id = Column(Integer,primary_key=True)18 name = Column(String(32),nullable=False)19 register_Date = Column(DATE,nullable=False)20 21 def __repr__(self):22 return "<%s name:%s>"% (self.id,self.name)23 24 class StudyRecord(Base):25 __tablename__ = "study_record"26 id = Column(Integer, primary_key=True)27 day = Column(Integer,nullable=False)28 status = Column(String(32),nullable=False)29 stu_id = Column(Integer,ForeignKey("student.id"))30 31 # 关系32 student = relationship("Student",backref="my_study_record")33 def __repr__(self):34 return "< day:%s status:%s>" % (self.id, self.status)35 36 37 Base.metadata.create_all(engine) # 创建表结构38 39 Session_class = sessionmaker(bind=engine) # 创建与数据库的会话session class 注意，这里返回的是一个class，不是实例40 41 session = Session_class()42 43 # s1 = Student(name="Tom",register_Date="2018-08-08")44 # s2 = Student(name="Jerry",register_Date="2018-06-08")45 # s3 = Student(name="Lucy",register_Date="2018-08-28")46 # s4 = Student(name="Lily",register_Date="2018-08-18")47 #48 # study_obj1 = StudyRecord(day=1,status="Yes",stu_id=1)49 # study_obj2 = StudyRecord(day=2,status="No",stu_id=1)50 # study_obj3 = StudyRecord(day=3,status="Yes",stu_id=1)51 # study_obj4 = StudyRecord(day=1,status="Yes",stu_id=2)52 53 # session.add_all([s1,s2,s3,s4,study_obj1,study_obj2,study_obj3,study_obj4])54 # session.commit()55 56 stu_obj = session.query(Student).filter(Student.name=="Tom").first()57 58 print(stu_obj.my_study_record) 解释：
（1）创建表：将43-54行代码解封，此时会自动为您创建相关联的表
重点理解：
32行：student = relationship("Student",backref="my_study_record")
这里需要引入 from sqlalchemy.orm import sessionmaker,relationship
32行代码用途，可以通过Student 在表StudyRecord中直接引用表Student 那么可以通过 my_study_record 直接引用StudyRecord中的数据。这是因为他们两者存在外键关联，所以当我们执行第58行的时候，他就会根据外键去查询study_record 中的数据。